Crusaders chief executive Hamish Riach describes the concept as "mouth-watering" but the already-congested rugby schedule is likely to make a cross-hemisphere competition unpalatable.

Suggestions of a new tournament involving top Super Rugby and England teams, who are reported to be unhappy with the Heineken Cup format, sound great but Riach says finding a window to play extra matches is a major stumbling block.

Although the Crusaders have not been contacted by any English clubs regarding this proposal, Riach said the franchise had "informal discussions" with Sanzar, the parent body which runs Super Rugby, about the idea.

"It will be interesting. As long as I have been in this job, we have been having this discussion," Riach said.

"But it has always proved too hard to put into a window."

There have been reports that English clubs are threatening to create a splinter tournament if their concerns around the Heineken Cup are not addressed.

In the past the Crusaders have fielded invites to play Heineken Cup champion sides but Riach said the clogged schedules prevented them being able to find a date.

"We couldn't even find a weekend for that. I am not sure when you can run this competition. Maybe this is something that needs to have the International Rugby Board, the national unions and Sanzar all involved."

Convincing the All Blacks to extend their workload will be another hurdle.

Last year several senior All Blacks voiced their concerns about burnout, stating they are playing too many matches. The New Zealand Rugby Union, in response to their feedback, are likely to play only three tests on their northern tour at the end of the year.

Yet Riach said the north-south competition should not be dismissed too quickly.